Add MemoryMapFileTruncated function

Change-Id: I26d2a9fbac668cbac284bdfad0d7912db521dc70

rocclr/os/os.hpp

@@ -120,6 +120,10 @@ class Os : AllStatic {
                                 const void** mmap_ptr);
   // Given a valid file name, returns mmapped memory with the mapped size.
   static bool MemoryMapFile(const char* fname, const void** mmap_ptr, size_t* mmap_size);
+
+  // Given a valid file name amd mapped size, returns ftruncated mmaped memory 
+  static bool MemoryMapFileTruncated(const char* fname, const void** mmap_ptr, size_t mmap_size);
+
   // Given a valid mmaped ptr with correct size, unmaps the ptr from memory
   static bool MemoryUnmapFile(const void* mmap_ptr, size_t mmap_size);
 

rocclr/os/os_posix.cpp

@@ -813,6 +813,31 @@ bool Os::MemoryMapFile(const char* fname, const void** mmap_ptr, size_t* mmap_si
   return true;
 }
 
+bool Os::MemoryMapFileTruncated(const char* fname, const void** mmap_ptr, size_t mmap_size) {
+  if ((mmap_ptr == nullptr)) {
+    return false;
+  }
+
+  struct stat stat_buf;
+  int fd = shm_open(fname, O_RDWR|O_CREAT, S_IRWXU|S_IRWXG|S_IRWXO);
+  if (fd < 0 ) {
+    return false;
+  }
+
+  if (ftruncate(fd, mmap_size) != 0) {
+    return false;
+  }
+  *mmap_ptr = mmap(NULL, mmap_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+
+  close(fd);
+
+  if (*mmap_ptr == nullptr) {
+    return false;
+  }
+
+  return true;
+}
+
 }  // namespace amd
 
 #endif  // !defined(_WIN32) && !defined(__CYGWIN__)

rocclr/os/os_win32.cpp

@@ -911,6 +911,10 @@ bool Os::MemoryMapFile(const char* fname, const void** mmap_ptr, size_t* mmap_si
   return true;
 }
 
+bool Os::MemoryMapFileTruncated(const char* fname, const void** mmap_ptr, size_t mmap_size) {
+  //TODO: fix with proper implementation
+  return false;
+}
 }  // namespace amd
 
 #endif  // _WIN32 || __CYGWIN__